GABA (gamma-aminobutyric acid) is the major inhibitory neurotransmitter in the mammalian nervous system. The fast synaptic inhibitory action of GABA is due largely to the activation of GABAA receptors, which are Cl- permeable ligand-gated ion channels. These receptors are also targets for several clinically important drug classes, including benzodiazepines, barbiturates, neurosteroids and general anesthetic. Moreover, modifications of GABAA receptor function are critical in a number of CNS pathologies including: epilepsy, anxiety, addiction, autism, and mental retardation. While the pharmacological manipulation of GABAA receptor function has been widely exploited clinically the endogenous mechanisms used by neurons to control the function and cell surface stability of these proteins remain unknown. However this issue is of central importance given the roles GABAA receptors play as mediators of synaptic inhibition, drug targets and in human disease. We hypothesize that the cell surface stability of GABAA receptors, is regulated via direct interactions with the AP2 complex, which plays an essential role in the recruitment of cargo into clathrin-coated pits to facilitate endocytosis. These interactions are dependent in turn on the phosphorylation status of GABAA receptors, which is subject to dynamic regulation by defined cell signaling pathways. Thus we will use a combination of cell biological, biochemical and electrophysiological approaches to carry out three independent but related specific aims: Specific Aim 1. To test the hypothesis that specific motifs mediate the interaction of GABAA receptors with the AP2 complex, and that these interactions are regulated by receptor phosphorylation. Specific Aim 2. To test the hypothesis that PKC activity regulates the phosphorylation, cell surface stability and activity of GABAA receptors. Specific Aim 3. To examine the significance of AP2 mediated endocytosis in the control of GABAA receptor cell surface stability. Together, our approaches will provide a more thorough understanding of the cell surface stability and function of GABAA receptors. The results of these studies will have the potential to make significant contributions to the development of novel therapeutic strategies for such debilitating disorders as epilepsy, anxiety, addiction, autism, and mental retardation.